在BroadCast Receiver中启动导致应用程序崩溃的活动

Question

我创建了一个应用程序，当我打开蓝牙时，会显示一个Toast并显示一个新的活动。这是我的广播接收机类：

public class BroadCast extends BroadcastReceiver { 

    String prefs="myPrefs"; 
    String count="myCount"; 
    static int counter=0; 
    Intent i; 

    @Override 
    public void onReceive(Context arg0, Intent arg1) { 
     String bluth = arg1.getAction(); 
     if (bluth.equals(BluetoothAdapter.ACTION_STATE_CHANGED)) { 
      if(arg1.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1) == BluetoothAdapter.STATE_ON){ 
       SharedPreferences sp = arg0.getSharedPreferences(prefs, Context.MODE_PRIVATE); 
       Editor ed = sp.edit(); 
       ed.putInt(count, counter); 
       ed.commit(); 
       counter++; 
       Toast.makeText(arg0, "Bluetooth on " + sp.getInt(count, 0), Toast.LENGTH_LONG).show(); 
       i = new Intent(arg0, Indicators.class); 
       i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 
       arg0.startActivity(i); 
       Indicators.on.setVisibility(View.VISIBLE); 
      } else if (arg1.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1) == BluetoothAdapter.STATE_OFF) { 

      } else if (arg1.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1) == BluetoothAdapter.STATE_TURNING_OFF) { 

      } else if (arg1.getIntExtra(BluetoothAdapter.EXTRA_STATE, -1) == BluetoothAdapter.STATE_TURNING_ON) { 

      } 
     } 
    } 
} 

现在没有问题了。当我把

Indicators.on.setVisibility(View.VISIBLE); 

运行应用程序，它崩溃！

其实on是我在Indicators class定义如下一个textview obj：

public class Indicators extends Activity { 
    static TextView on, off, opening, closing; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     // TODO Auto-generated method stub 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.textviewbluetooth); 

     opening = (TextView)findViewById(R.id.textView1); 
     on = (TextView)findViewById(R.id.textView2); 
     closing = (TextView)findViewById(R.id.textView3); 
     off = (TextView)findViewById(R.id.textView4); 
     opening.setVisibility(View.INVISIBLE); 
     on.setVisibility(View.INVISIBLE); 
     off.setVisibility(View.INVISIBLE); 
     closing.setVisibility(View.INVISIBLE); 
    } 
} 

我应该如何消除这种错误？

Answer 1

class YourActivity extends xxxx { 
    private static YourActivity mInst; 

    public static YOurActivity instance() { 
      return mInst; 
    } 

    /// Do your task here. 
    public void setViewText(xxxx) ; 

    @Override 
    public void onStart() { 
    ... 
    mInst = this; 
    } 

    @Override 
    public void onStop() { 
    ... 
    mInst = null; 
    } 
} 

而在你的广播接收器：

YOurActivity inst = YOurActivity.instance(); 
    if(inst != null) { // your activity can be seen, and you can update it's context 
     inst.setViewText... 
    } 

Answer 2

把这一行

   on.setVisibility(View.VISIBLE); 

活动内部 - > onCreate（）方法。

不要在Activity本身外部使用对Activity类成员（如TextViews）的静态引用，因为它可能已被销毁，或者尚未创建。一般来说这是不好的做法。

编辑：如果您需要标志来显示指标，请在活动起始者意向中添加一个额外内容。